Tensile energy accumulator and shock absorbing device for well pipe strings



Sept. 20, 1960 D. D. WEBB 2,953,352

TENSILE ENERGY AccuMuLAToR AND sHocK ABsoRBING DEVICE Foa WELL PIPESTRINGS f Filed Aug. 4, 195e INVENTOR @4f/eea .0. Wf

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ATTORNEY Patented Sept. 20, 1960 United States PatentOfiice TENSILEENERGY ACCUMULTOR AND lSHOCK ABSORBING DEVICE FOR WELL PIPE STRINGSDerrel Dee Webb, Houston, Tex., assigner to Houston Engineers, Inc.,Houston, Tex., a corporation of Texas Filed Aug. 4, 1958, Ser. No.752,987

11 Claims. (Cl. Z55- 28) go. to a great depth in the earth, the drillingtools are attached to the lower end of a pipe string which isloweredrwithin the well and provides the driving connection for the`drilling tools.V Occasionally, either the tools or the pipe becomejammed4 or wedged in the well and it is sometimes exceedingly diflicultto remove such parts from the well in order to repair the Ysame andresume drilling operations. Where a direct pullV from the surface isinsuilicient to dislodge the stuck parts, it has been cus'- tornary toutilize what. is commonly known as a jarring tool. which ineliectyprovides a succession of hammer blows in an axial direction tofree the parts and permit withdrawal of the same from the Well. o

The jarring tool is normally interposed in the pipe string relativelyclose to the drilling tools and in operation when it is desired toremove partsY which khave become jammed in the well bore, a strongupward force is applied to the pipe string and thereafter the jarringtool is actuated to impart hammer blows tothe same in order to free thestuck parts and permit withdrawalof the same from the well bore. Theoperation of the jarring tool imparts extremely high impact loads orshock to the well string, as well as to the jammed tool or other partwedged in the well and also tothe hoisting equipmentrat the surface.Such shock materially reduces the life of the well equipment and alsoreduces the effectiveness of the jarring operation. It has also beenfound that the effectiveness of conventional jarring tools is materiallyreduced when such tools are utilized in a well bore which is crooked orhas been drilled at an angle to the vertical, since the jarring effectis absorbed in the pipe string and is not applied in its full intensityto the object to be removed. s

It is accordingly an object of the invention to provide a tensile energyaccumulator and shock absorbing device which may be convenientlyinstalled in well pipe strings without requiring any modificationwhatsoever, and which operates to materially increase the eciency ofjarring tools also installed in the pipe string.

A further object of the invention is the provision of a tensile energyaccumulator and shock absorbing device for well pipe strings whichoperates to store tensile energy and release the same on the actuationof a jarring tool and at the same time, operates to absorb shock causedby operation of such jarring tool.

A still further object of the invention is the provision of a tensileenergy accumulator and' shock absorbing device for well pipe stringswhich may be installed in the string adjacent a jarring tool Yand inwhich relative movement caused by operation of the jarring tool islsubstantially confined to the section between theupper end of theenergy'accumulator and shock absorbing device and the tool or other'object to be removed from the well, thereby maintaining the eliiciencyof the jarring device and preventing absorption of the force exertedtherebyV by the pipe string disposed in a well having a crooked bore orone drilled at an angle to the vertical.

Another object of the invention is the provision of a tensile energyaccumulator and shock absorbing device for well pipe strings which maybe conveniently installed in such pipe string and which will in no wayinterfere with normal drilling operations.

A further object ofthe invention is the provision of a tensile energyaccumulator and shockk absorbing device for well pipe strings utilizinga compressible non-combustible uid for accumulating and storing tensileenergy and also incorporating a valve controlled means for facilitatingintroduction of such compressible uid into the device. s

A stillr further object of the invention is the provision of a tensileenergy accumulator and shock absorbing device for well pipe stringswhich may be conveniently and economically manufactured from readilyavailable materials and which may be conveniently utilized withconventional jarring tools and other well equipment.

`Further objects and advantages of the invention will be apparent fromthe following description taken in conjunction with the accompanyingdrawing wherein:

"Fig la is a longitudinal sectional view of the upper half of a tensileenergy accumulator and shock absorbing device'constructed in accordancewith this invention;

Fig. 1b a longitudinal sectional view showing the lower half of the toolshownin Fig. la;

Fig. 2 `a sectional view taken substantially on the line 2,:-2 of Fig.la; and

Fig. 3 a fragmentary sectional Iview showing the means for facilitating'introduction of compressible fluid into the toolfof this invention.

` With continued reference' to the drawing, there is shown a tensileenergyaccumul'ator'and shock absorbing device constructed in accordancewith' this invention and which may. wellcomprise an elongated'v tubularbody 10 having 1arniupper section 11,y a central section 12 and a lowersectionl',V Y The upper section 11 is provided with a collar 14threadedly received' in the upper end thereof and the collar 14 servesto` provide a downwardly facing abutment 15 within the upper section 11.The collar v14 is provided with splines 1'6 which' inter-engage withsplines l1,7 on a hollow mandrel 18 which is slidably received in thecollar 14 and upper section 11`. The mandrel 18 is provided at thefupper end with conventional screw threaded means l9`for facilitatingconnecting the same to a wellv pipe string and the mandrel 18 isprovided with a fluid passage 20 extending therethrough. The splines116. and 17 serve to Vprevent relative rotation between the mandrel 18andthe body 10, but permit sliding movement ofthe mandrel 18 within thecollar 14 and upper section 11. A coupling member 21 is secured to thelower end of the mandrel 18 by screw threaded or other suitablefasteningmeans 22 and the coupling member 21 serves to provide anupwardly facing shoulder 23 and a downwardly facing shoulder 24. Ventopenings 25 and 26 are provided in the upper and lower ends respectivelyof the upper section 11 and serve to release any uid whichmay collecttherein which might otherwise impede vertical movement of the mandrel 18within the upper section 11. g

A coupling section 27 serves to connect theupper section 11andthecentral section 12 and the coupling section 27 maybe secured' tothe' upper section 11 by screw threaded' or otherisuitableffasteningmeans 28l and this coupling'section 27 serves-to' provide an upwardlyfacingabutment 29 in the lower end of the upper section 11. Theabutments and 29 serve to limit axial vertical movement of the mandrel18 within the upper section 11, the upper limit of movement beingreached when the shoulder 23 engages the abutment 15 andthe lower limitof movement being reached when the shoulder 24 engages the abutment 29on the coupling section 27. The coupling section 27 is connected to thecentral Section 12 by screw threaded or other suitable fastening means30 and if desired, suitable packing means 31 may be provided in thejoint between the coupling section 27 and the central section 12 inorder to prevent leakage of uid through this joint.

A hollow plunger 32 is connected to the coupling member 21 by screwthreaded or other suitable fastening means 33 and the plunger 32 extendsthrough the coupling section 27 and the central section 12 andterminates at its lower end 34 within the lower section 13. The plunger32 is provided with a passage 35 extending therethrough in axialalignment with the passage in the mandrel 18.

An elongated cylindrical chamber -36 is provided in the central section12 and a piston 37 on the plunger 32 is provided with packing means 38for providing a uid tight engagement between the piston 37 and the wallof the chamber 36.

As best shown in Fig. 3, the upper portion of the central section 12 isprovided with a transverse bore 39 extending to the exterior thereof andin alignment with the bore 39 is a threaded counterbore 40 for receivinga valve plug 41 which may be manipulated to open or close the bore 39.Communicating with the counterbore 40 outwardly of the valve seat 42 isa threaded bore 43 normally closed by a threaded plug 44 but uponremoval of the plug 44, a source of compressible non-combustible lluidmay be connected to the threaded bore 43 and upon opening of the valveplug 41, such fluid may be forced into the chamber 36 to fill the samewith uid above the piston 37 at any desired pressure. Closure of thevalve plug 41 against the seat 42 will permit removal of the source ofuid and insertion of the closure plug 43 without the loss of fluid fromthe chamber 36.

Fluid tight packing means 45 is provided in the coupling section 27engaging the plunger 32 to prevent leakage of uid from the chamber 36 tothe interior of the upper section-11 and a fluid tight packing means 46is provided in the upper portion of the lower section 13 engaging theplunger 32 to prevent leakage of fluid `from the chamber 36 into thelower section 13. The lower section 13 is provided with conventionalscrew threaded means 47 for detachably connecting the lower section 13to a jarring tool or other equipment disposed in the well above thejarring tool.

In operation, the tensile energy accumulator and shock absorbing deviceof this invention is installed in a well pipe string with the mandrel 18connected to the lower end of the well pipe string by means of thethreaded connection 19 and with the lower section 13 of the deviceconnected by means of the connection 47 to a jarring tool or otherequipment in the well above the jarring tool. The chamber 36 is filledwith a compressible noncombustible fluid to the desired pressure andduring normal drilling operations, the piston 37 on the plunger 32 willbe located adjacent the lower end of the chamber 36 as clearly shown inFig. lb.

Upon the drilling tool or other equipment below the device of thisinvention becoming wedged or stuck in the well, an upward force isexerted on the mandrel 18 by hoisting equipment at the surface and suchupward force operates to move the mandrel 18 and plunger 32, as well asthe piston 37 upwardly to compress the fluid in the upper portion of thechamber 36 until the upward pulling force is balanced by the pressurefluid in such chamber 36. This will also serve to exert an upward forceon the jarring tool and equipment wedged in the well. Actuation of thejarring tool will serve to impart a sudden impact or hammer blow to theequipment below the device of this invention which will result inmovement of the body 10 upwardly with relation to the plunger 32 andmandrel 18 and during such upward movement, the energy stored in thecompressed fluid in the chamber 36 will be expended to maintain anupward `force on the jarring tool and other equipment in the well belowthe device of this invention and this relative movement between the body1% and they plunger 32 and mandrel 18 will serve to absorb the shock tothe pipe string and equipment above the device of this invention whichwould normally be caused by actuation of the jarring tool. Thisoperation may be repeated as many times as necessary to free the stuckequipment.

it will be seen that by the above described invention, there has beenprovided a device which serves as a cushion between a jarring tool and awell pipe string and hoisting equipment, as well as a device for storingtensile energy which may be expended upon actuation of the jarring toolto maintain the eciency of such jarring tool, regardless of the freedomof movement of the equipment above such tool, which movement might beimpeded by a crooked well bore or one drilled at an angle from thevertical and furthermore such device will operate to absorb the shockresulting from actuation of the jarring tool. The device of thisinvention may be utilized with conventional jarring tools and other wellequipment without necessitating modification thereof and will alsooperate to materially increase the life and maintain the eiciency ofsuch equipment.

It will be obvious to those skilled in the art that various changes maybe made in the invention without departing from the spirit and scopethereof and therefore the invention is not limited by that which isshown in the drawing and described in the specification, but only asindicated in the appended claims. What is claimed is:

l. A tensile energy accumulator and shock absorbing device for well pipestrings, said-device comprising an elongated tubular body having anupper section, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said mandrel fordetachably connecting a well pipe string, a collar threadedly receivedin the upper end of said upper section surrounding said mandrel andproviding a downwardly facing abutment within said upper section,inter-engaging splines on said collar and mandrel to prevent relativerotation between said mandrel and body, a coupling member secured to thelower end of said mandrel within said upper section and providingupwardly and downwardly facing shoulders, a coupling section betweensaid upper section and said central section and providing an upwardlyfacing abutment in said upper section, engagement of said-shoulders withsaid abutments serving to limit axial movement of said mandrel in saidupper section, a hollow plunger connected to said coupling memberextending through said coupling section and said central section andterminating within said lower section, an elongated cylindrical chamberin said central section, a piston on saidplunger having a fluid tightsliding engagement with the wall of said chamber, coupling and valvemeans in the upper portion of said central section for facilitating theintroduction of a compressible fluid into said chamber above saidpiston, fluid tight packing means in said coupling section engaging saidplunger to prevent leakage of fluid from said chamber to said uppersection,uid tight packing means in the upper portion of said lowersection engaging said plunger to prevent leakage of fluid from saidchamber to said lower section and meanson the lower end of said lowersection for detachably connecting a jarring tool, whereby uponexertingan upward force on said mandrel said plunger and piston will moveupwardly to compress einem y fluid in said chamber and impose an upwardforce on said jarringl tool and upon actuation of said jarringrtoolsaidbody will `move upwardly relative to said plunger and piston to expendthe energy stored in the compressed fluid and absorb shock caused bysaid jarring tool.

2. A device as defined in claim 1 in which said upper section isprovided with vent apertures adjacent the upper and lower ends thereofto permit release of fluid within said upper section.

3. A tensile energy accumulator and shock -absorbing device for wellpipe strings, said device comprising an elongated tubular body having anupper sect-ion, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said vmandrel fordetachably connecting a well pipe string, a collar threadedly receivedin the upper end of said upper section surrounding said mandrel andproviding a downwardly facing abutment within said upper section,inter-engaging splines on said collar and mandrel to lprevent relativerotation between said mandrelv and body, a coupling member secured tothe lower end of said mandrel within said upper section and providingupwardly and downwardly facing shoulders, a coupling section betweensaid upper section and said central section and providing an upwardlyfacing abutment in said upper section, engagement of said shoulders withsaid abutments serving to limit axial movement of said mandrel in saidupper section, a hollow plunger connected to said coupling memberextending through said coupling section and said central section andterminating within said lower section, an elongated cylindrical chamberin s-aid central section, a piston on said plunger having a fluid tightsliding engagement with the wall of said chamber, means in the upperportion of said central section for facilitating the introduction of acompressible tluid into said chamber above said piston, lluid tightpacking means in said coupling section engaging said plunger topreventleakage of fluid from said chamber togsaid upper section, fluid tightpacking means in the upper portion of said lower section engaging saidplunger to prevent leakage of Huid from said chamber to said lowersection and means on the lower end of said lower section for detachablyconnecting a jarring tool, whereby upon exerting an upward force on saidmandrel said plunger and piston will move upwardly to compress fluid insaid chamber and impose an upward force on said jarring tool and uponactuation of said jarring tool said body will move upwardly relative tosaid plunger andV piston to expend the energy stored in the compresseduid and -absorb shockv caused by said jarring tool.

4. A tensile energy accumulator and shock absorbing device for well pipestrings, said device comprising an elongated tubular body having anupper section, a central'section andl a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said mandrel fordetachably connecting a well pipe string, a collar secured in the upperend of said upper section surrounding said mandrel and providing adownwardly `facing abutment within said upper section, means to preventrelative rotation between said mandrel and body, a coupling membersecured to the lower end of said mandrel within said upper section andproviding upwardly and downwardly facing shoulders, a coupling sectionVbetween said upper section and said central section and providing anupwardly facing abutment in said upper section, engagement of saidshoulders with said abutments serving to limit axial movement of saidmandrel in said upper section, a hollow plunger connected to saidcoupling member extending through said coupling section and said centralsection and terminating within said lower section, an elongatedcylindrical chamber in ysaid central section, a kpiston on said plungerhaving a I fluid tight sliding engagement with the wall of Vsaidchamber,means in the upperv portion of said vcentral section for facilitatingthe introduction of a compressible fluid into Vsaid chamber above saidpiston, fluid tight packing means in said coupling section engaging saidplunger to prevent leakage of uid from said chamber to saidr uppersection, fluid tight packing means inthe upper portion of said lowersection engaging said plunger to prevent leakage of uid from saidchamber to said lower section and means on the lower end of said lowersection for detachably connecting a jarring tool, whereby upon exertingan upward force on said mandrel said plunger and piston will moveupwardly to compress fluid in said chamber and impose an upward force onsaid jarring tool and upon actuation of said jarring tool said body willmove upwardly relative'to said plunger and .piston to` expend the energystored in the compressed'uid and absorb shock caused by said jarringtool.

- 5. A tensile energy accumulator and shock absorbing device for wellpipe strings, said device comprising an elongated tubular body having anupper section, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said mandrel fordetachably connecting a well pipe string, a collar secured ini the upperend of said upper section surrounding said mandrel and providing adownwardly facing abutment within said upper section, means to preventrelative rotation between said mandrel and body, a coupling membersecured to the lower end of said mandrel within said upper section andproviding upwardly and downwardly facing shoulders, a coupling sectionbet-Ween said upper section and said central section and providing anupwardly facing abutment in said upper section, engagement of saidshoulders with said abutment serving to limit axial movement of saidmandrel. in said uppersection, ay hollow plunger connected to saidcoupling member extending throughy said coupling section and saidcentral section and into said lower section,:an elongated cylindricalchamber in said central section, a piston on said plunger having a iiuidtight sliding engagement with ythe wall of said chamber, means `in theupper portion of said central section for facilitating the introductionof a compressible uid intousaid chamber above said piston, fluid tightpacking means in saidcoupling. section engaging said plunger toprevent'leakage of tluid from said chamber to said upper section,tiuidtight packing means in the upper rportion of said lower sectionengaging said plunger to prevent leakage of tluid from said chamber tosaid lower section and means Aon the lower end of said lower section fordetachably connect- .ing va jarringftool, whereby upon exerting anupward force on said mandrel said plunger and piston will move upwardlyto compress fluid in said chamber and impose an .upward force on saidjarring tool and upon actuation of said jarring tool said body will moveupwardly relative to said plunger and piston to expend the energy storedin the compressed fluid and absorb shock caused` by said jarring tool.

6. A tensile energy accumulator and shock absorbing device for wellVpipe strings, saidf device comprising kan elongated tubular bodyhavingfan upper section, a centralrsectionand` alower section, saidsections being detachably secured together, a hollow mandrel slidablyreceived insaid upper section, means on the upper 'end of said mandrelfor detachably connecting arwell pipe string, means to prevent relativerotatonbetween said mandrel and body, a couplingmember secured to thelower end of said mandrel within said upper section, a coupling sectionbetweenfsaid upper section and said central section, means to limitaxial movement of said mandrel in said upper section, ak hollow plungerconnected to said coupling member extending through said couplingsection and said central section and into said lower section, anelongated cylindrical chamber in said central section, a piston onv saidplunger having a fluid tight sliding engagement-with the wall of saidchamber, means inthe upper portion of said central section forfacilitating the introduction of a compressible fluid into said chamberabove said piston, fluid tight packing means in said coupling sectionengaging said plunger to prevent leakage of fluid from said chamber tosaid upper section, fluid tight packing means in the upper portion ofsaid lower section engaging said plunger to prevent leakage of fluidfrom said chamber to said lower section and means on the lower end ofsaid lower section for detachably connecting a jarring tool, wherebyupon exerting an upward force on said mandrel said plunger and pistonwill move upwardly to compress uid in said chamber and impose an upwardforce on said jarring tool and upon actuation of said jarring tool saidbody will move upwardly relative to said plunger and piston to expendthe energy stored in the compressed fluid and absorb shock caused bysaid jarring tool.

7. A tensile energy accumulator and shock absorbing device for well pipestrings, said device comprising an elongated tubular body having anupper section, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said mandrel fordetachably connecting a well pipe string, means to prevent relativerotation between said mandrel and body, a coupling member secured to thelower end of said mandrel within said upper section, means to limitaxial movement of said mandrel in said upper section, a hollow plungerconnected to said coupling member extending through said couplingsection and said central section and into said lower section, anelongated cylindrical chamber in said central section, a piston on saidplunger having ra fluid tight sliding engagement with the wall of saidchamber, means for facilitating the introduction of a compressible fluidinto said chamber above said piston, iiuid tight packing means in saidcoupling section engaging said plunger to prevent leakage of fluid fromsaid chamber to said upper section, fluid tight packing means in theupper portion of said lower section engaging said plunger to preventleakage of fluid [from said chamber to said lower section and means onthe lower end of said lower section for de tachably connecting a jarringtool, whereby upon exerting an upward force on said mandrel said plungerand piston will move upwardly to compress fluid in said chamber andimpose an upward force on said jarring tool and upon actuation of saidjarring tool said body will move upwardly relative to said plunger andpiston to expend the energy stored in the compressed fluid and absorbshock caused by said jarring tool.

8. A tensile energy accumulator and shock absorbing device for well pipestrings, said device comprising an elongated tubular body having anupper section, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said mandrel fordetachably connecting a well pipe string, means to prevent relativerotation between said mandrel and body, a coupling member secured to thelower end of said mandrel, a coupling section between said upper sectionand said central section, a hollow plunger connected to said couplingmember extending through said coupling section and said central sectionand into said lower section, an elongated cylindrical chamber inV saidcentral section, a piston on said plunger having a tuid tight slidingengagement with the wall of said chamber, means for facilitating theintroduction of a compressible fluid into said chamber above saidpiston, uid tight packing means in said coupling section engaging saidplunger to prevent leakage of fluid from said chamber to said uppersection, fluid tight packing means in the upper portion of said lowersection engaging said plunger to prevent leakage of fluid from saidchamber to said lower section and means on the lower end of said lowersection :for detachably connecting a jarring tool, whereby upon exertingan upward force on said mandrel said plunger and piston will moveupwardly to compressV lluidV in said chamber and impose an upward forceon said jarring tool and upon actuation of said jarring tool said bodywill move upwardly relative to said plunger and piston to expend theenergy stored in the compressed 'uidrand absorb shock caused by saidjarring tool.

9. A tensile energy accumulator and shock absorbing device for well pipestrings, said device comprising an elongated tubular body having anupper section, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, Imeans on the upper end of said mandrel fordetachably connecting a well pipe string, means to prevent relativerotation between saidmandrel and `said body, a coupling member securedto the lower end of said mandrel, a coupling section between said uppersection and said central section, a hollow plunger connected to saidcoupling member extending through said coupling section and said centralsection and into said lower section, an elongated cylindrical chamber insaid central section, a piston on said plunger having a iiuid tightsliding engagement with the wall of said chamber, means for facilitatingthe introduction of a compressible uid into said chamber above saidpiston, means -to prevent leakage of iluid from said chamber to saidupper section, means to prevent leakage of uid from said chamber to saidlower section and means on the lower end of sa-id lower section fordetachably connecting a jarring tool, whereby upon exerting an upwardforce on said mandrel, said plunger and piston will move upwardly tocompress iiuid in said chamber and impose an up ward force on saidjarring tool and upon actuation of said jarring tool said body will moveupwardly relative to said plunger and piston to expend the energy storedin the compressed fluid and Vabsorb shock caused by said jarring tool.

l0. A tensile energy accumulator and shock absorbing device for wellpipe strings, said device comprising an elongated tubular body having anupper section, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said mandrel fordetachably connecting a well pipe string, means to prevent relativerotation between said mandrel and body, a coupling member secured to thelower end of said mandrel, a hollow plunger connected to said couplingmember extending through said central section and into said lowersection, an elongated cylindrical chamber in said central section, apiston on said plunger having a iiuid tight sliding engagement with thewall of said chamber, means for facilitating the introduction of acompressible fluid into said chamber above said piston, means to preventleakage of iluid from said chamber to said upper section, means toprevent leakage of fluid from said chamber lto said lower section andmeans on the lower end of said lower section for detachably connecting ajarring tool, whereby upon exerting an upward force on said mandrel saidplunger and piston will move upwardly to compress fluid in said chamberand impose an upward force on said jarring tool and upon actuation ofsaid jarring tool said body will move upwardly relative to said plungerand piston to expend the energy stored in the compressed iluid andabsorb shock caused by said jarring tool.

ll. A tensile energy accumulator and shock absorbing device for wellpipe strings, said device comprising an elongated tubular body having anupper section, a central section and a lower section, said sectionsbeing detachably secured together, a hollow mandrel slidably received insaid upper section, means on the upper end of said mandrel fordetachably connecting a well pipe string, means to prevent relativerotation between said mandrel and body, a coupling member secured to thelower find, 0f Said mandrel, a hollow plunger connected to said couplingmember extending through said central section and into said lowersection, an elongated cylindrical chamber in sa-id central section, apiston on said plunger having a uid tight sliding engagement with thewall of said chamber, means for facilitating the introduction of acompressible fluid into said chamber labove said piston and means on thelower end of said lower section for detachably connecting a jarringtool, whereby upon exerting an upward force on said mandrel said plungerand piston will move upwardly to compress Huid in said chamber andimpose anupward force on said jarring References Cited in the le of thispatent UNITED STATES PATENTS 1,804,700 Maxwell May 12, 1931 10 2,544,473Smith Mar. 6, 1951 2,585,995 Brown Feb. 19, 1952

